Continuous variable valve lift apparatus

ABSTRACT

A continuously variable valve lift apparatus may include an input unit, a camshaft for receiving rotation from the input unit, wherein one end portion of the camshaft is slidably coupled to the input unit in a longitudinal direction of the camshaft, a controlling unit for controlling a relative position of the camshaft in the longitudinal direction of the camshaft, a slanted cam disposed to the camshaft and a cross-section of which is slanted with a predetermined angle with respect to a longitudinal axis of the camshaft, a mediating unit slanted with substantially the same angle of the slanted cam and pivoting in response to rotation of the slanted cam, and a valve opening unit that is opened/closed in response to the pivoting motion of the mediating unit.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2008-0040846 filed Apr. 30, 2008, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a continuous variable valve lift apparatus, and more particularly to a continuous variable valve lift apparatus that can adjust a valve lift amount in response to an operational state of an engine

2. Description of Related Art

A typical combustion chamber of an automotive engine is provided with an intake valve for supplying an air/fuel mixture and an exhaust valve for expelling burned gas. The intake and exhaust valves are opened and closed by a valve lift apparatus connected to a crankshaft.

A conventional valve lift apparatus has a fixed valve lift amount due to a fixed cam shape. Therefore, it is impossible to adjust the amount of gas that is being introduced or exhausted.

If the valve lift apparatus is designed for low driving speeds, the valve open time and amount are not sufficient for high speeds. On the other hand, if the valve lift apparatus is designed for high speeds, the opposite is true.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

BRIEF SUMMARY OF THE INVENTION

Various aspects of the present invention are directed to provide a continuous variable valve lift apparatus having increased operation range of valve lift and to provide a continuous variable valve lift apparatus that may realized with a small number of elements and may be reduced a total size thereof.

In an aspect of the present invention, a continuously variable valve lift apparatus may include an input unit, a camshaft for receiving rotation from the input unit, wherein one end portion of the camshaft is slidably coupled to the input unit in a longitudinal direction of the camshaft, a controlling unit for controlling a relative position of the camshaft in the longitudinal direction of the camshaft, a slanted cam disposed to the camshaft and a cross-section of which is slanted with a predetermined angle with respect to a longitudinal axis of the camshaft, a mediating unit slanted with substantially the same angle of the slanted cam and pivoting in response to rotation of the slanted cam, and/or a valve opening unit that is opened/closed in response to the pivoting motion of the mediating unit.

The input unit may include a camshaft sprocket slidably coupled to the one end portion of the camshaft, and/or an elastic member disposed between the camshaft sprocket and the camshaft and supplying restoring force to the camshaft toward the controlling unit. The elastic member may be a spring.

The one end portion of the camshaft may have a shape of an oval cross-section, a polygon, or a spline.

The camshaft may include a cam connecting portion formed at the one end portion of the camshaft to be slidably coupled to the camshaft sprocket. The cam connecting portion may have a shape of an oval cross-section, a polygon, or a spline.

The input unit may further include a front journal connected to the camshaft sprocket, and the camshaft are slidably coupled to the front journal in the longitudinal direction of the camshaft. The one end portion of the camshaft may have a shape of an oval cross-section, a polygon, or a spline. The camshaft may include a cam connecting portion formed at the one end portion of the camshaft to be slidably coupled to the front journal of the input unit. The cam connecting portion may have a shape of an oval cross-section, a polygon, or a spline.

The controlling unit may include an eccentric cam that contacts the other end portion of the camshaft for controlling the relative position of the camshaft. Rotation angle of the eccentric cam may be controlled by a control unit.

The mediating unit may include a rocker shaft disposed in parallel to the camshaft, and/or a rocker lever rotatably coupled to the rocker shaft and slidably contacting the slanted cam. The rocker lever may be biased toward the camshaft by an elastic member. The elastic member may be a spring.

The rocker lever may include a slanted portion slidably contacting the slanted cam, and/or an output portion slidably contacting the valve opening unit. The output portion may include a lift section that generates valve lift in response to pivoting of the rocker lever, and/or a zero lift section that does not generate the valve lift, allowing pivoting of the rocker lever.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary continuously variable valve lift apparatus according to the present invention.

FIG. 2 is a front view of an exemplary continuously variable valve lift apparatus according to the present invention.

FIG. 3 is a drawing showing some elements of an exemplary continuously variable valve lift apparatus according to the present invention.

FIG. 4 is a drawing showing an operation of an exemplary continuously variable valve lift apparatus according to the present invention in low lift mode.

FIG. 5 is a drawing showing an operation of an exemplary continuously variable valve lift apparatus according to an the present invention in high lift mode.

FIG. 6 is a graph showing an exemplary profile characteristic of a variable valve lift apparatus according to an the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 and FIG. 2 are a perspective view and a front view respectively of a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention.

FIG. 3 is a drawing showing main elements of a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 1 to FIG. 3, a variable valve lift apparatus according to an exemplary embodiment of the present invention includes an input unit 100 that receives a torque, a camshaft 200 that receives rotation force from the input unit 100 and is movably disposed along a longitudinal direction thereof, and a controlling unit 300 for controlling a relative position of the camshaft 200 along the longitudinal direction thereof.

A slanted cam 210 is disposed to the camshaft 200, wherein a cross-section the slanted cam 210 is slanted along the longitudinal direction of the camshaft 200. That is, the slanted cam 210 is preferably formed as a crushed and truncated cone.

Rotation force of the slanted cam 210 is transmitted to a mediating unit 400 which is slanted and pivots by the slanted cam 210, and then to a valve opening unit 500 in response to pivoting of the mediating unit 400.

In an exemplary embodiment of the present invention, the input unit 100 includes a front journal 120, and the camshaft 200 and the front journal 120 are slidably coupled along the longitudinal direction with respect to each other and transmit rotation to the camshaft 200.

That is, as shown in FIG. 3( b) and (c), a front journal connecting portion 125 and a camshaft connecting portion 205 are formed to connect to each other, and the front journal connecting portion 125 and the camshaft connecting portion 205 may transmit rotation of the input unit 100 and may be slidably movable along a longitudinal direction with respect to each other.

In the drawing, the front journal connecting portion 125 and the camshaft connecting portion 205 are described as being oval, however, they are not limited to the described shape. General polygon or a spline can be used for the front journal connecting portion 125 and the camshaft connecting portion 205.

In another exemplary embodiment of the present invention, one end portion of the camshaft 200 may be formed to be oval, polygon, or a spline so that the end portion of the camshaft 200 can be slidably coupled to the front journal 120 without the camshaft connecting portion 205.

The input unit 100 further includes a camshaft sprocket 110 and an elastic member 130 that is disposed between the camshaft sprocket 110 and the front journal 120 for supplying a restoring force to the camshaft 200.

The controlling unit 300 includes an eccentric cam 310 that contacts the other end portion of the camshaft 200 for controlling a relative position of the camshaft 200 in a longitudinal direction thereof.

The eccentric cam 310 is controlled by an ECU (electronic control unit; not shown) that detects and determines operation states of an engine, and operations of the ECU and angle change of the eccentric cam 310 can be adjusted in accordance with performance requirements of an engine. Operations of an engine and angle change of the eccentric cam 310 can be variable according to performance requirements of an engine and can be realized by a person skilled in the art referring to the detailed description, so a detailed explanation will be omitted.

The mediating unit 400 includes a rocker shaft 410 in parallel to the camshaft 200 and a rocker lever 420 that is pivotally coupled to the rocker shaft 410. In an exemplary embodiment of the present invention, the rocker lever 420 may be biased toward the camshaft 200 by an elastic member 450 disposed at the rocker shaft 410.

The rocker lever 420 includes a slanted portion 422 contacting the slanted cam 210 and an output portion 424 contacting the valve opening unit 500.

The output portion 424 includes a lift section 426 that generates valve lift to the valve opening unit 500 in response to pivoting of the rocker lever 420 and a zero lift section 428 that does not generates valve lift, allowing pivoting of the rocker lever.

That is, when the lift section 426 contacts the valve opening unit 500, a valve 510 is opened, but when the zero lift section 428 contacts the valve opening unit 500, the valve 510 is not opened.

Hereinafter, operations of the continuously variable valve lift apparatus according to an exemplary embodiment of the present invention will be explained.

FIG. 4 is a drawing showing operation of a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention in low lift mode, and FIG. 5 is a drawing showing operation of a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention in high lift mode.

The lift mode and lift timing depend on inclination ratio of the slanted cam 210 and the slanted portion 422 of the rocker lever 420 and an eccentric rate of the eccentric cam 310 as explained hereinafter.

As shown in FIG. 4, in the low lift mode for a small load, the eccentric cam 310 rotates for the camshaft 200 to be more distant from the slanted portion 422 of the rocker lever 420. Accordingly the distance between the camshaft 200 and a contact point of the slanted cam 210 and the rocker lever 420 is decreased such that the rocker lever 420 pivots in the clockwise direction in FIG. 2. Due to the clockwise pivoting motion, the zero lift section 428 of the rocker lever 420 comes in contact with the valve opening unit 500. Therefore, the valve lift and lift timing of the valve 510 are reduced.

That is, as shown in FIG. 2, the time that the zero lift section 428 contacts the valve opening unit 500 is increased.

When in the high lift mode for a large load, as shown in FIG. 5, the eccentric cam 310 rotates for the slanted cam 210 of the camshaft 200 to be close to slanted portion 422 of the rocker lever 420.

As shown in FIG. 4, in the high lift mode for a large load, the eccentric cam 310 rotates for the slanted cam 210 of the camshaft 200 to be close to the slanted portion 422 of the rocker lever 420. Accordingly the distance between the camshaft 200 and a contact point of the slanted cam 210 and the rocker lever 420 is increased such that the rocker lever 420 pivots in the counterclockwise direction in FIG. 2. Due to the counterclockwise pivoting motion, the lift section 426 of the rocker lever 420 comes in contact with the valve opening unit 500. Therefore, the valve lift and lift timing of the valve 510 are increased.

That is, as shown in FIG. 2, the time that the zero lift section 428 contacts the valve opening unit 500 is reduced and the time that the lift section 426 contacts the valve opening unit 500 is increased.

FIG. 6 is a graph showing a profile characteristic of a variable valve lift apparatus according to an exemplary embodiment of the present invention.

As shown in FIG. 6, the continuously variable valve lift apparatus according to an exemplary embodiment of the present invention may realize an optimal valve profile with simple operations of the eccentric cam and inclination of the slanted cam and slanted portion.

Also, a simple design change of the output portion 424 may realize CDA (cylinder deactivation) mode. Accordingly the continuously variable valve lift apparatus according to an exemplary embodiment of the present invention may reduce production cost and maintain cost with a simple structure and a small number of elements.

The entire size of the continuously variable valve lift apparatus according to an exemplary embodiment of the present invention may be reduced with a compact scheme.

For convenience in explanation and accurate definition in the appended claims, the term “front” is used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

1. A continuously variable valve lift apparatus comprising: an input unit; a camshaft for receiving rotation from the input unit, wherein one end portion of the camshaft is slidably coupled to the input unit in a longitudinal direction of the camshaft; a controlling unit for controlling a relative position of the camshaft in the longitudinal direction of the camshaft; a slanted cam disposed to the camshaft and a cross-section of which is slanted with a predetermined angle with respect to a longitudinal axis of the camshaft; a mediating unit slanted with substantially the same angle of the slanted cam and pivoting in response to rotation of the slanted cam; and a valve opening unit that is opened/closed in response to the pivoting motion of the mediating unit.
 2. The continuously variable valve lift apparatus of claim 1, wherein the input unit comprises: a camshaft sprocket slidably coupled to the one end portion of the camshaft; and an elastic member disposed between the camshaft sprocket and the camshaft and supplying restoring force to the camshaft toward the controlling unit.
 3. The continuously variable valve lift apparatus of claim 2, wherein the elastic member is a spring.
 4. The continuously variable valve lift apparatus of claim 2, wherein the one end portion of the camshaft has a shape of an oval cross-section, a polygon, or a spline.
 5. The continuously variable valve lift apparatus of claim 2, wherein the camshaft includes a cam connecting portion formed at the one end portion of the camshaft to be camshaft coupled to the camshaft sprocket.
 6. The continuously variable valve lift apparatus of claim 5, wherein the cam connecting portion has a shape of an oval cross-section, a polygon, or a spline.
 7. The continuously variable valve lift apparatus of claim 2, wherein the input unit further comprises a front journal connected to the camshaft sprocket, and the camshaft are slidably coupled to the front journal in the longitudinal direction of the camshaft.
 8. The continuously variable valve lift apparatus of claim 7, wherein the one end portion of the camshaft has a shape of an oval cross-section, a polygon, or a spline.
 9. The continuously variable valve lift apparatus of claim 7, wherein the camshaft includes a cam connecting portion formed at the one end portion of the camshaft to be slidably coupled to the front journal of the input unit.
 10. The continuously variable valve lift apparatus of claim 9, wherein the cam connecting portion has a shape of an oval cross-section, a polygon, or a spline.
 11. The continuously variable valve lift apparatus of claim 1, wherein the controlling unit comprises an eccentric cam that contacts the other end portion of the camshaft for controlling the relative position of the camshaft.
 12. The continuously variable valve lift apparatus of claim 11, wherein rotation angle of the eccentric cam is controlled by a control unit.
 13. The continuously variable valve lift apparatus of claim 1, wherein the mediating unit comprises: a rocker shaft disposed in parallel to the camshaft; and a rocker lever rotatably coupled to the rocker shaft and slidably contacting the slanted cam.
 14. The continuously variable valve lift apparatus of claim 13, wherein the rocker lever is biased toward the camshaft by an elastic member.
 15. The continuously variable valve lift apparatus of claim 14, wherein the elastic member is a spring.
 16. The continuously variable valve lift apparatus of claim 13, wherein the rocker lever comprises: a slanted portion slidably contacting the slanted cam; and an output portion slidably contacting the valve opening unit.
 17. The continuously variable valve lift apparatus of claim 16, wherein the output portion comprises: a lift section that generates valve lift in response to pivoting of the rocker lever; and a zero lift section that does not generate the valve lift, allowing pivoting of the rocker lever.
 18. An passenger vehicle comprising the continuously variable valve lift apparatus of claim
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